TW202337636A - Heterogeneous fluoropolymer mixture polishing pad - Google Patents

Abstract

The invention provides a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic or electromechanical substrates. The polishing pad includes a polyurea polishing layer and a polyurea matrix. The polyurea matrix has a soft phase and a hard phase. The soft phase is formed from soft segments and the hard phase is formed from diisocyanate hard segments and a curative agent. The soft segment areva copolymer of aliphatic fluorine-free polymer groups and a fluorocarbon having a length of a least six carbons. The polyurea matrix is cured with the curative agent and includes gas or liquid-filled polymeric microelements. The soft segments form a fluorine rich phase that concentrates adjacent the polymeric microelements and at the polishing layer during polishing. The polishing layer remains hydrophilic during polishing in shear conditions.

Description

Heterogeneous Fluorinated Polymer Blend Polishing Pads

The present invention relates to a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic or electromechanical substrates.

Chemical mechanical planarization (CMP) is a variation of the polishing process that is widely used to planarize or flatten the structural layers of integrated circuits to accurately construct multi-layer three-dimensional circuits. The layer to be polished is typically a thin film (less than 10,000 Angstroms) that has been deposited on the underlying substrate. The purpose of CMP is to remove excess material from the wafer surface to produce an extremely flat layer of uniform thickness throughout the entire wafer area. Controlling the removal rate and uniformity of removal is critical.

CMP uses a liquid (often called a slurry) containing nanometer-sized particles. It is fed onto the surface of a rotating multi-layered polymer sheet or pad mounted on a rotating platen. The wafers are mounted into separate holders or holders with separate rotational devices and pressed against the surface of the pad under a controlled load. This results in high relative motion rates between the wafer and polishing pad (i.e., high shear rates at both the substrate and pad surfaces). Slurry particles trapped at the pad/wafer junction can abrade the wafer surface, causing removal. To control the rate, prevent water slippage, and efficiently deliver slurry beneath the wafer, various types of textures are incorporated into the upper surface of the polishing pad. Fine textures are produced by using fine diamond array polishing pads. This is done to control and increase the removal rate and is often called trimming. Larger proportions of grooves (e.g., XY, circular, radial) in various patterns and sizes are also incorporated for fluid dynamics and slurry transport regulation.

It is widely observed that the removal rate during CMP follows the Preston equation, rate = K _p *P * V, where P is the pressure, V is the velocity, and K _p is the so-called Preston coefficient. The Preston coefficient is a summation constant that is characteristic of the consumable group used. Several of the most important effects that contribute to _K are as follows: (a) pad contact area (mainly from pad texture and surface mechanical properties); (b) slurry particle concentration on the surface of the contact area available for work; and (c) ) the reaction rate between surface particles and the surface of the layer to be polished. The effect (a) depends largely on the characteristics of the pad and the dressing process. Effect (b) depends on the pad and slurry, while effect (c) depends heavily on the slurry properties.

The emergence of high-capacity multi-layer memory devices such as 3D NAND flash memory has led to the need to further increase the removal rate. A key part of _the 3D NAND manufacturing process involves stacking multiple layers of _SiO2 and _Si3N4 films alternately in a pyramid-shaped staircase. Once completed, the stack is covered with a thick _SiO2 capping layer, which must be planarized before completing the device structure. This thick film is often called a pre-metal dielectric (PMD). Device capacity is proportional to the number of layers in the layered stack. Current commercial installations use 32 and 64 layers, and the industry is rapidly evolving to 128 layers. The thickness of each oxide/nitride pair in the stack is approximately 125 nm. Therefore, the thickness of the stack increases directly with the number of layers (32 = 4,000 nm, 64 = 8,000 nm, 128 = 16,000 nm). For the PMD step, assuming PMD conformal deposition, the total amount of cover dielectric to be removed is approximately equal to approximately 1.5 times the thickness of the stack.

The removal rate of conventional dielectric CMP slurries is approximately 250 nm/min. This creates undesirably long CMP processing times for the PMD step, which is currently a major bottleneck in the 3D NAND manufacturing process. Therefore, there has been much work on developing faster CMP processes. Most improvements have focused on process conditions (higher P and V), changing pad trimming processes, and improving slurry design, especially _CeO2 -based slurries. If an improved pad could be developed that could be paired with existing processes and _CeO slurries to achieve higher removal rates without any negative impacts, it would constitute a significant improvement in CMP technology.

The most commonly used top pad in dielectric CMP is the IC1000™ polyurethane polishing pad. This pad has a number of desirable properties, including its surface charge in water. As shown in Sokolov et al. (J. Colloid Interface Sci, 300 (2), p.475-81, 2006), when the pH value is greater than 2, the IC1000™ polishing pad has The surface charge becomes increasingly negative. Because the polishing pad is in motion during polishing, the physical properties of the pad roughness under shear are critical.

The main methods used to achieve increased rates in CMP pads are as follows: i) Optimizing the groove design without changing the top pad composition; ii) Changing the trimming process without changing the top pad composition; iii) Borrowing providing the pad with a more desirable dressing response by modifying the dressing response of the top pad; and iv) pads providing a top pad with higher stiffness or improved elastic properties.

Hattori et al. (Proc. ISET07, p.953-4 (2007)) present a plot of zeta potential versus pH for various lanthanide particle dispersions, including _CeO2 . The pH of zero charge, or isoelectric point, is measured to be about 6.6. Below this pH, the particle has a positive potential; above this pH, the particle has a negative potential. For modifications of different ceria particles or ceria-containing slurries, the isoelectric point may shift.

With the development of 3D NAND, the demand for polishing pads with improved ceria polishing rates has increased.

Embodiments of the present invention provide a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic or electromechanical substrates, comprising: a polyurea polishing layer comprising a polyurea matrix, the polyurea polishing layer The urea matrix has a soft phase and a hard phase. The soft phase is formed by a soft segment, and the hard phase is formed by a diisocyanate hard segment and a curing agent. The soft segment is an aliphatic fluorine-free polymer group. and a copolymer of a fluorocarbon having a length of at least six carbons, the polyurea matrix being cured by the curing agent and containing gas or liquid filled polymeric microelements, the soft segments forming during polishing to aggregate adjacent the A fluorine-rich phase at the polymeric microelements and polishing layer that remains hydrophilic during polishing under shear conditions.

Another embodiment of the present invention provides a polishing pad suitable for polishing at least one of a semiconductor, optical, magnetic or electromechanical substrate, comprising: a polyurea polishing layer comprising a polyurea matrix, The polyurea matrix has a soft phase and a hard phase, the soft phase is formed by soft segments, and the hard phase is formed by diisocyanate hard segments and a curing agent and wherein the hard phase is precipitated in the soft phase, The soft segment is a copolymer of aliphatic fluorine-free polymer groups and a fluorocarbon having a length of at least six carbons, the polyurea matrix is cured by the curing agent and contains gas or liquid filled polymer microelements , the soft segments form a fluorine-rich phase that accumulates adjacent to the polymeric microelements and the polishing layer during polishing, wherein the polishing layer remains hydrophilic during polishing under shear conditions.

The polishing pad of the present invention is suitable for polishing at least one of semiconductor, optical, magnetic or electromechanical substrates. A key element of the present invention is to modify the surface properties of the top pad to drive the ceria slurry or other particles above their isoelectric point for polishing with the upper surface or polishing layer. In particular, the present invention increases the effectiveness or efficiency of the ceria slurry particles on the upper surface, increasing the polishing rate. An unexpected and novel effect of the pad of the present invention is that the fluorocopolymer is added to the soft segment of the polyurethane block copolymer at a relatively low concentration (approximately 1-20 wt% of the total soft segment concentration). Improved removal rate. For purposes of this application, all amounts are in weight percent unless specifically stated otherwise. Preferably, the concentration of fluorinated species is 8 to 30 wt% of the total fluorinated species plus the content of aliphatic fluorine-free polymer groups in the soft segment. Additionally, polishing pads must use polishing pads that are hydrophilic during polishing to achieve improved performance. Obtaining a polishing pad that is hydrophilic during polishing helps achieve a thin and effective pad-wafer gap for effective polishing. Additionally, an unexpected effect of adding fluorocopolymer is a reduction in the pad's electronegativity, or zeta potential, making the pad surface very hydrophilic during polishing.

In view of the above, the unexpected discovery of the present invention is that by selectively adding a small percentage of fluorinated polymer segments to the soft segments of the polyurethane block copolymer, it is possible to realize water in a very low surface energy mat. The zeta potential is increased and the removal rate of slurries with cationic particles (such as CeO ₂ ) is increased. More specifically, as shown in Figure 1, the addition of fluorinated soft segment components produces significant phase separation, forming fluorine-rich regions (dark gray) and fluorine-poor regions (light gray and white). Figure 1 shows fluorine-rich regions with higher and lower fluorine concentrations around polymeric microelements. However, the fluorine-rich regions illustrated in dark gray are almost entirely concentrated in adjacent chlorine-containing polymer microspheres illustrated in black. The migration of this fluorine-rich phase into the microelements forms the heterogeneous mixture microstructure of the present invention. The thickness of the fluorine-rich phase adjacent the microspheres is less than fifty percent of the average diameter of the polymeric microelements. Also unexpected was the accumulation of the fluorine-rich soft phase at the polished surface. This soft phase appears to smear and cover most of the polished surface. Most polyureas illustrated in light gray and white illustrate the fluorocarbon-containing polyurea matrix.

In block polyurethane copolymers, rigid hard segments provide stiffness and have a high glass transition temperature (Tg). Soft segments generally have a low Tg and are more flexible at room temperature. Phase separation occurs due to immiscibility between hard and soft segments. In addition, biuret crosslinking groups connect some of the soft segments to the hard segments. The biuret has the formula _R2NC (O)NR'C(O)NHR", where _R2 is a soft segment, R' includes an aromatic ring and R" includes an aromatic ring.

The polishing pad has a polyurea polishing layer. The polyurea polishing layer includes a polyurea matrix including a soft phase and a hard phase. The soft phase is formed from a soft segment having two or more aliphatic fluorine-free polymer groups and at least one fluorinated species having two end groups. Typically, fluorinated species have a length of at least six carbon atoms. Preferably, the fluorinated species is at least eight carbon atoms in length. Most preferably, the fluorinated species is at least ten carbon atoms in length. The aliphatic fluorine-free polymer groups are bonded to both end groups of at least one fluorinated substance via nitrogen-containing bonds. Examples of nitrogen-containing linkages include urea groups and polyurethane groups. The aliphatic fluorine-free polymer group has one end attached to at least one fluorinated species via a nitrogen-containing bond. Typically, the aliphatic fluorine-free polymer groups have a number average molecular weight between 200 and 7500. For purposes of clarity, aliphatic fluorine-free polymer groups terminate before isocyanate end groups (such as toluene diisocyanate) and do not include isocyanate end groups, nitrogen-containing linkages, or amine curing agents. Most preferably, the aliphatic fluorine-free polymer groups have a number average molecular weight between 250 and 5000 as measured after reaction with the amine curing agent. Isocyanate groups cap the reactive ends of the aliphatic fluorine-free polymer groups. The soft segments form a soft phase in the polyurea matrix. Most preferably, the aliphatic fluorine-free polymer groups are polytetramethylene ether linked to a fluorinated species. The fluorinated substance may contain at least one kind of fluorinated ethers. Preferably, the fluorinated material contains fluorinated ethylene oxide, fluorinated oxymethylene and ethylene oxide. Most preferably, the atomic ratio of fluorinated ether groups such as fluorinated ethylene oxide and fluorinated oxymethylene to ethylene oxide is less than 3.

The hard phase system is formed from a diisocyanate-containing hard segment that does not contain fluorine groups and an amine-containing curing agent. The hard segment contains urea groups formed from an isocyanate group at the outer end of the blocked aliphatic fluorine-free polymer group and an amine-containing curing agent. Preferably, the hard segments precipitate as a hard phase within the soft phase. This morphology provides a fluorine-rich phase for enhanced ceria interaction and a hard phase for strengthening the soft phase to improve polish asperity integrity, thereby increasing pad life and stability when polishing multiple wafers sex. Preferably, the hard and soft segments form a prepolymer which is then reacted with an amine-containing curing agent to form a polyurea matrix. The presence of the fluoride moiety in the soft segment increases the glass transition temperature of the soft segment or the Tg of the soft phase. This unexpected increase in glass transition temperature improves the thermal stability of the polymer. At the uppermost surface of the polymer in air, an enrichment of the fluorinated soft segment components occurs during polishing. This in situ and continuous generation of fluorine-rich phases at the surface further enhances the beneficial effects of small amounts of fluorinated polymers. At fairly low fluorinated soft segment concentrations (e.g., less than 20 wt% of the total soft segment content), the amount of fluorinated species is insufficient to prevent the polymer from subsequently being exposed to water, especially under shear. Dipole rearrangement of water molecules. This results in complex wetting behavior when the droplets are sheared. Specifically, it is believed that water surface rearrangement allows for increased interaction of water with the hydrophilic portion of the polymer. This causes a decrease in the droplet's receding contact angle and a corresponding increase in surface energy during polishing. As a result, under shear, the polishing pads of the present invention can be even more hydrophilic than their fluorine-free analogues.

It is generally accepted that fluorinated polymers such as polytetrafluoroethylene (PTFE) have a high negative zeta potential in water, typically greater than -20 mV, and have poor surface wetting by aqueous solutions in the absence of suitable wetting agents. Strong resistance. [For the purposes of this specification, zeta potential is a general term for the potential adjacent a charged surface. Zeta potential measurements can vary significantly depending on the device, device settings, and a variety of other factors. ] However, the potential explanation for the high negative zeta potential of PTFE is simply due to the high degree of orientation of the water dipole at the polymer surface and the low surface polarity.

For the polishing pads of the present invention, the liquid-solid contact angle dynamic method represents the best technique for measuring contact angle. This is because polishing is a dynamic process in which water experiences shearing forces between a wafer rotating at one speed and an increasing diameter polishing pad rotating at another speed. Differences in diameter cause the surfaces to move in the same, opposite, partially identical and partially opposite directions. Due to varying velocities, all polishing fluids between the wafer and polishing pad experience a range of shear forces. For a moving droplet, the advancing contact angle represents the degree of liquid/solid bonding, while the receding contact angle represents the degree of liquid/solid adhesion. Generally, the advancing contact angle is significantly higher than the receding angle. The degree of difference between the two is called contact angle hysteresis. Contact hysteresis in surface wetting can be affected by many factors. The main effects are caused by surface roughness (e.g. lotus leaf effect), contaminants, surface inhomogeneities, the extent of solvent/surface interactions (including hydrogen bonding and direct reactions) and shear rate. Regardless of other factors, the surface energy of a solid increases directly with increasing shear rate due to contact hysteresis. In the case of a set of materials with identical surfaces, the increase in contact hysteresis is a direct measure of the increase in solvent/surface attraction (i.e., the surface is more hydrophilic for water) and is consistent with wetting as measured by differences in surface polarization. Sexually related. Importantly, the polishing pads of the present invention are hydrophilic as measured by increased wettability as receding contact angle when polishing under shear conditions. In particular, the polishing layer is hydrophilic during polishing under shear conditions, as shown by receding angle tests with deionized water and diiodomethane.

The CMP polishing pad according to the present invention can be manufactured by the following method, which includes: providing an isocyanate-terminated polyurethane prepolymer; separately providing a curing agent component; and combining the isocyanate-terminated polyurethane prepolymer and the curing agent component to form Combining; reacting the combination to form a product; forming a polishing layer from the product, such as by scraping the product to form a polishing layer of a desired thickness and such as by machining the same to groove the polishing layer, and forming a polishing layer having a polishing layer Chemical mechanical polishing pads.

The pad of the present invention is a polyurea block copolymer containing both hard segments and soft segments. The isocyanate-terminated polyurethane prepolymer used in the formation of the polishing layer of the chemical mechanical polishing pad of the present invention preferably includes: the reaction product of components, including: multifunctional isocyanate and containing two or more components ( One of them is a fluorinated) prepolymer mixture.

Preferably, the isocyanate is a diisocyanate. More preferably, the multifunctional isocyanate is a diisocyanate selected from the group consisting of: 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; 4,4' diphenylmethane diisocyanate; naphthalene- 1,5-diisocyanate; toluidine diisocyanate; p-phenylene diisocyanate; xylylene diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4'-dicyclohexylmethane diisocyanate Isocyanates; cyclohexane diisocyanate; and mixtures thereof. Most preferably, the diisocyanate is toluene diisocyanate.

Optionally, the aliphatic fluorine-free polymer groups are selected from the group consisting of diols, polyols, polyol diols, copolymers thereof, and mixtures thereof. For example, an aliphatic fluorine-free polymer group can be reacted with a diisocyanate and the fluorinated species can then be linked to the diisocyanate. Specifically, the prepolymer polyol may be selected from the group consisting of: polyether polyols (such as poly(oxytetramethylene) glycol, poly(oxypropyl) glycol, poly(oxyethylene) glycol. polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of: ethylene glycol Alcohol; 1,2-propanediol; 1,3 propanediol; 1,2-butanediol; 1,3-butanediol; 2-methyl 1,3-propanediol; 1,4-butanediol; neopentyl glycol alcohol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. Still more preferably, the prepolymer polyol is selected from the group consisting of at least one of the following: polytetramethylene ether glycol (PTMEG); polypropylene ether glycol (PPG); and polypropylene ether glycol (PPG). Ethyl ether glycol (PEG); optionally mixed with at least one low molecular weight polyol selected from the group consisting of: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,2- Butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1 ,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. Most preferably, the prepolymer polyol is primarily (ie, ≥ 90 wt %) polytetramethylene ether. Fluorinated polyols may be formed by displacement addition from any of the unfluorinated polyols cited above. This results in minimal changes in the final mechanical properties.

Preferably, the isocyanate-terminated polyurethane prepolymer has an unreacted isocyanate (NCO) concentration of 8.5 to 9.5 wt %. Examples of commercially available isocyanate-terminated polyurethane prepolymers include Imuthane™ prepolymers (available from COIM USA, Inc.), such as PET-80A, PET-85A, PET-90A, PET- 93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene™ prepolymer (available from Chemtura, such as LF 800A, LF 900A, LF 910A, LF-930A, LF-931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Andur™ prepolymers (available from Anderson Development Corporation (Anderson Development Company), such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF).

Preferably, the isocyanate-terminated polyurethane prepolymer is a low free isocyanate-terminated polyurethane prepolymer with a free toluene diisocyanate (TDI) monomer content of less than 0.1 wt%.

The curing agent component used in the formation of the polishing layer of the CMP polishing pad of the present invention optionally contains a polyol curing agent or a multifunctional aromatic amine curing agent, such as a bifunctional curing agent. Examples of commercially available polyol curing agents include Specflex™ polyols, Voranol™ polyols, and Voralux™ polyols (available from The Dow Chemical Company). These multifunctional curing agents contain at least three hydroxyl groups to increase cross-linking of the polymer.

Preferably, the bifunctional curing agent is selected from diols and diamines. More preferably, the bifunctional curing agent used is a diamine selected from the group consisting of primary amines and secondary amines. Still more preferably, the bifunctional curing agent used is selected from the group consisting of: diethyltoluenediamine (DETDA); 3,5-dimethylthio-2,4-toluenediamine and its isomers structure; 3,5-diethyltoluene-2,4-diamine and its isomers (e.g., 3,5-diethyltoluene-2,6-diamine); 4,4'-bis- (Secondary butylamino)diphenylmethane; 1,4-bis-(secondary butylamino)-benzene; 4,4'-methylene-bis-(2-chloroaniline); 4, 4'-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA); polytetramethylene oxide-bis-p-aminobenzoate; N,N-bis Alkyldiaminodiphenylmethane; p,p'-methylenediphenylamine (MDA); m-phenylenediamine (MPDA); 4,4'-phenylene-bis(2-chloroaniline) (MBOCA ); 4,4'-methylene-bis-(2,6-diethylaniline) (MDEA); 4,4'-methylene-bis-(2,3-dichloroaniline) (MDCA) ;4,4'-Diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane; 2,2',3,3-Tetrachlorodiaminodiphenylmethane ; Trimethylene glycol di-p-aminobenzoate; and mixtures thereof. Most preferably, the diamine curing agent used is selected from the group consisting of: 4,4'-methylene-bis(2-chloroaniline) (MBOCA); 4,4'-methylene- Bis-(3-chloro2,6-diethylaniline) (MCDEA); and its isomers.

The polishing layer of the chemical mechanical polishing pad of the present invention may further include a plurality of micro-elements. Preferably, the microelements are evenly dispersed throughout the polishing layer. Preferably, the microelements are selected from the group consisting of trapped air bubbles, hollow polymeric materials, liquid-filled hollow polymeric materials, water-soluble materials, and insoluble phase materials (eg, mineral oil). More preferably, the plurality of microelements are selected from trapped air bubbles and hollow polymer materials evenly dispersed throughout the polishing layer. Preferably, the plurality of microelements have a weight average diameter of less than 150 µm (more preferably equal to or less than 50 µm; most preferably 10 to 50 µm). Preferably, the plurality of microelements are polymeric microspheres having shell walls of polyacrylonitrile or vinylidene chloride-polyacrylonitrile copolymer (eg Expancel™ microspheres from Akzo Nobel) . Preferably, a plurality of microelements are incorporated into the polishing layer with a porosity of 0 to 50 vol. % (preferably, a porosity of 10 to 35 vol. %). The vol. % porosity is determined by dividing the difference between the specific gravity of the unfilled polishing layer and the specific gravity of the polishing layer containing microelements by the specific gravity of the unfilled polishing layer.

Referring to Figure 2, the polymeric microelements in the transition region adjacent to the polishing layer decrease in thickness as they approach the polishing layer. Below the transition region, the polymer microelements remain intact and do not break like spherical microelements. The polymeric microspheres are closed-cell or non-reticular. But as polymer microspheres near a polished surface, they break and compress into smaller, non-spherical microelements. The force behind this consolidation of the polymer microspheres appears to be the associated compression of the polishing head and dresser before penetrating the microspheres with diamond or another abrasive. However, most dressing discs rely on diamonds mounted on or otherwise secured to a metal plate. The microspheres were not fractured by diamond trimming as can be seen by the undisturbed surface texture adjacent to the compressed or fractured microspheres. Therefore, the cause of polymer microsphere rupture is not related to diamond puncture caused by diamond dressing. In particular, Figure 3 shows compressed microspheres at higher magnification. As polishing wears the polishing pad, the microspheres adjacent to the polishing layer compress to a thickness less than their original diameter. Typically, this thickness is less than fifty percent of the original diameter; and it can be less than thirty percent of the original diameter. Another unexpected feature of the present invention is that compression of the polishing pad during polishing forms adjacent interconnected channels and the polymer microspheres break up at the polishing layer. This is a local phenomenon that occurs only adjacent to the polished surface. The remaining microspheres remain closed-cell or intact until the pad wears a sufficient amount to bring the microspheres close to the polished surface. This appears to release fluid from within the microspheres and allow additional compression of the microspheres before piercing them with a diamond dresser.

The polishing layers of the CMP polishing pads of the present invention can be provided in both porous and non-porous (ie, unfilled) constructions. Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention exhibits a density of 0.4 to 1.15 g/cm ³ (more preferably, 0.70 to 1.0 g/cm ³ ; measured according to ASTM D1622 (2014)) .

Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention exhibits a Shore D hardness of 28 to 75 as measured according to ASTM D2240 (2015).

Preferably, the polishing layer has an average thickness of 20 to 150 mils (0.05 to 0.4 cm). More preferably, the polishing layer has an average thickness of 30 to 125 mils (0.08 to 0.3 cm). Still more preferably, the polishing layer has an average thickness of 40 to 120 mils (0.1 to 0.3 cm); most preferably, 50 to 100 mils (0.13 to 0.25 cm).

Preferably, the CMP polishing pad of the present invention is adapted to be connected to the platen of a polishing machine. Preferably, the CMP polishing pad is adapted to be fixed to the platen of the polishing machine. Preferably, the CMP polishing pad may be secured to the platen using at least one of a pressure sensitive adhesive and a vacuum.

The CMP polishing pad of the present invention optionally further includes at least one additional layer connected to the polishing layer. Preferably, the CMP polishing pad optionally further includes a compressible base layer adhered to the polishing layer. The compressible base layer preferably improves the conformability of the polishing layer to the surface of the substrate being polished.

The final form of the CMP polishing pad of the present invention also includes texture incorporated into one or more dimensions on its upper surface. These can be classified as macrotextures or microtextures based on their size. Conventional types of macrotexturing are used in CMP to control hydrodynamic response and slurry transport, and include, but are not limited to, grooves with many configurations and designs, such as annular, biased radial, and hatched lines. These may be formed into uniform sheets by a machining process, or may be formed directly on the pad surface by a net shape forming process. Common types of microtexture are finer-scale features that create significant surface roughness at the points of contact with the substrate wafer where polishing occurs. Common types of microtexture include, but are not limited to, texture formed by grinding with arrays of hard particles such as diamond (commonly referred to as pad dressing) before, during, or after use, and microstructure formed during the pad manufacturing process. texture.

As can be seen from Figure 4, a small tooth-like polished surface similar to shark skin can be formed during the diamond dressing process. This microtexture is extremely fine and may further explain improved polishing removal rates. This effect is particularly noticeable when polishing using cationic particles such as ceria particles.

An important step in the substrate polishing operation is to determine the end point of the process. A common in situ method for end point detection involves providing a polishing pad with a window that is transparent to selected wavelengths of light. During polishing, a beam is directed through a window to the substrate surface where it is reflected and passed through the window back to a detector (eg, a spectrophotometer). Based on the returned signal, the characteristics of the substrate surface (eg, film thickness thereon) can be determined for endpoint detection purposes. To facilitate such light-based endpoint methods, the chemical mechanical polishing pads of the present invention optionally further include an endpoint detection window. Preferably, the endpoint detection window is selected from the group consisting of integrated windows incorporated into the polishing layer; and plug-in endpoint detection window blocks incorporated into the chemical mechanical polishing pad. For unfilled pads of the present invention with sufficient transmittance, the overlying pad layer itself can serve as the window aperture. Since the pads of the present invention exhibit phase separation, it is also possible to create transparent areas of the top pad material by locally increasing the cooling rate during the manufacturing process to locally inhibit phase separation, thereby creating more transparent areas suitable for use as termination windows. .

As described in the Background of the Invention, CMP polishing pads are used with polishing slurries. The CMP polishing pad of the present invention is designed for use with slurries having a pH lower than the isoelectric pH of the particles used. For example, _CeO2 has an isoelectric point pH of about 6.6. Below this pH, the particle surface has a net positive charge. Above this pH, particles have a net negative charge. Because the pads of the present invention exhibit a high negative charge at this pH, an increase in rate is achieved when the particles are below the isoelectric point.

The CMP pad of the present invention can be manufactured by a variety of methods that are compatible with thermosetting polyurethane. Such methods include mixing the above ingredients and casting into molds, annealing, and then cutting into sheets of desired thickness. Alternatively, they can be manufactured in a more precise net shape form. According to the preferred method of the present invention, it includes: 1. Thermosetting injection molding (commonly known as "reaction injection molding" or "RIM"); 2. Thermoplastic or thermosetting injection blow molding; 3. Compression molding; or 4. Any similar type of process in which a flowable material is positioned and solidified thereby producing at least a portion of the macrotexture or microtexture of the pad. In the preferred molding embodiment of the invention: 1. the flowable material is forced into or onto the structure or substrate; 2. the structure or substrate imparts surface texture to the material as it solidifies, and 3. then Separating the structure or substrate from the cured material.

Some embodiments of the invention will be described in detail in the following examples. Example

The pad samples used in the examples were prepared as follows: Materials

PTMEG is a blend of various PTMEGs from Invista with molecular weights ranging from 250 to 2000. 4,4'-Dicyclohexylmethane diisocyanate/toluene diisocyanate ("H ₁₂ MDI/TDI") PTMEG is an Adiprene™ L325 prepolymer from Lanxess with 8.95 to 9.25 wt% NCO. TDI is available from Dow as Voranate™ T-80. The polymer microspheres are Expancel™ vinylidene chloride-polyacrylonitrile copolymer microspheres, which have an average particle size of approximately 20 µm. Fluorinated polymers are ethoxylated perfluoroethers. The fluorinated polymer has a linear structure of ethylene oxide-terminated fluorinated ethylene oxide-fluorinated oxymethylene. The "R" atomic ratio of fluorinated ethers to ethylene oxide is 1.9 or 5.3. Prepolymer synthesis

Prepolymers were synthesized in batches ranging from about 200 to 1000 grams. Ethoxylated perfluoroethers are added by replacing a portion of the PTME2000 component of the prepolymer to produce varying levels of fluorinated polytetramethyl ether. Mix TDI and H ₁₂ MDI in a weight ratio of 80:20 before adding to the mixture. Sufficient isocyanate mixture is then added to the mixture to achieve the desired NCO wt%. The entire mixture was mixed again and then placed in a preheated oven at 65°C for 4 hours before use. All samples were tested on the day of synthesis. pad production

The synthesized prepolymer and 4,4′-dicyclohexylmethane diisocyanate/toluene diisocyanate (“H ₁₂ MDI/TDI”) polytetramethylene ether were heated to 65°C. MBOCA was pre-weighed and melted in an oven at 110°C. After a reaction time of 4 hours or once heated, the polymer microspheres were added to the prepolymer and the polymer microspheres in the prepolymer were degassed by vacuum. All filled samples included a distribution of polymer microspheres sufficient to achieve specific gravity or final density. After degassing, and once both components have reached temperature, MBOCA is added to the prepolymer and mixed. After mixing, the sample was poured onto a hot plate and stretched using Teflon™-coated rods set to 175 mils (4.4 mm) apart. The plates were then transferred to the oven and heated to 104°C and kept at this temperature for 16 hours. The drawdown films were then demolded and stamped to 22" (55.9 cm) and used to prepare laminate pads for polishing. All pads were 20" (50.8 cm) in diameter with 80 mil (2.0 mm) Top Pad, 1010 Circular Grooves with Width, Depth and Spacing of 20 Mil, 30 Mil and 120 Mil (0.51 mm, 0.76 mm and 3.05 mm) respectively, Pressure Sensitive Adhesive Film for Sub Pad, Suba IV™ Polyurethane Impregnated Polyester Pad and Pressure Sensitive Pressure Plate Adhesive. Plates for each material group were also made with and without polymer microsphere filler for property testing.

A reference table for the samples cited in the following examples is given in Table 1. Fluorinated polymer content in controls expressed as percent substitution of PTMEG content using 4,4'-methylene-bis(2-chloroaniline) measured as 105% NCO versus cured amine stoichiometry A mixture of cured polyether toluene diisocyanate-terminated liquid prepolymers (NCO 8.9 to 9.3 wt%). For the purposes of this specification, stoichiometry refers to the molecular ratio of NCO to amine.

[Table 1] sample Ethoxylated perfluoroether (Wt. %) A 0 1 6 2 12 3 18 4 twenty four Example 1

Samples of polyurea formulations with varying degrees of fluorinated substitution were prepared. Comparative A is a fluorine-free parent material; while Samples 1 and 2 were produced with 6 wt% and 12 wt% of the polytetramethylene ether component replaced by fluorinated substances. Plate samples produced without fillers showed a significant decrease in clarity at both fluoropolymer content levels, indicating a greater degree of phase separation. Furthermore, FTIR analysis showed the presence of biuret, with a peak at 1535 cm ^-1 .

A summary of the material properties of the three materials is given in Table 2. Performance differences at substitution levels of 12 wt% or less are relatively small. However, at higher replacement levels, the pads become increasingly brittle. The functional limit of reduced elongation and toughness without undesirable effects on the polishing process is estimated to occur at approximately 20 wt% substitution. [Table 2] sample Ethoxylated perfluoroether wt% Density (g/cm ³ ) durometer hardness Median tensile strength (MPa) Median elongation (%) Median modulus (MPa) Toughness (MPa) A 0% 0.93 64D 24.4 166 334.4 37.8 1 6% 0.96 65D 32.4 198 417.4 57.9 2 12% 0.91 65D 32.0 138 459.6 41.9 3 18% 1.01 66D 30.3 77 403.8 21.6 4 twenty four% 1.01 68D 32.0 55 458.9 15.7 Note: Samples 1 to 4 have a perfluoroether/ethylene oxide atomic ratio of approximately 1.9. Example 2

A useful range of pad surface properties relative to a fluorine-free matrix was examined. The measured properties are both static and dynamic contact angle measurements to derive the surface energy. Plate samples were used for both sets of measurements to ensure measurements were taken on a smooth as-cast surface. This avoids measurement errors caused by surface roughness. This is most critical for surface energy measurements.

Surface energy measurements were performed by the sessile drop method using commercial equipment manufactured by Kruss. Measurements were performed using deionized water and diiodomethane/methylene iodide. Surface energy values were derived from measured average contact angles using the two-component Fowkes method. Both static and dynamic measurements are made to derive equilibrium, advancing and receding surface energies. Dynamic contact angle [Table 3] sample Minimum surface energy (calculated from advancing angle) (dynes /cm ) Maximum surface energy (calculated from receding angle) (dynes /cm ) γ _s ^d γ _s ^p γ _s ^total γ _s ^d γ _s ^p γ _s ^total A 28.8 1.0 29.8 50.8 16.7 67.5 2 11.1 1.9 13.0 46.5 15.7 62.2 3 11.5 1.4 12.9 47.4 13.3 60.7

Assuming a contact angle of 0 (completely wetted by diiodomethane), the control pad becomes hydrophilic under dynamic conditions. Surprisingly, the data show that samples 2 and 3, which have large amounts of fluorinated polymer and high electronegativity, are also hydrophilic under dynamic conditions. This test verifies that the polishing pad is hydrophilic during polishing. Example 3

Pads of the invention were prepared with different specific gravities, and with 8.9 to 9.3 wt% cured with 4,4'-methylene-bis(2-chloroaniline) with a stoichiometry of NCO measured as 105% to cured amine. A second mixture of NCO's polyethertoluene diisocyanate-terminated liquid prepolymer ("Comparative Sample B") was used to polish TEOS wafers using both slurries.

The first slurry was a commercially available ceria slurry (Asahi CES333F) prepared using the manufacturer's instructions. The pH during use is 5.5. Based on previous data, a pH well below the isoelectric point pH of the ceria particles used was used. The second slurry was also a commercially available silica slurry (Cabot SS25) prepared using the manufacturer's instructions. The pH during use is 10.5. Based on the data presented previously, a pH well above the isoelectric point of the silica particles used was used.

Each pad was used to polish the wafer over a range of applied pressures using the same conditions, allowing estimation of differences in Preston coefficients, as measured by the slope of the pressure versus rate response. The polishing conditions used for each test were a platen speed of 93 rpm, a wafer carriage speed of 87 rpm, and a slurry flow rate of 200 ml/min. The polishing equipment used was the Mirra™ tool from Applied Materials.

As shown in Table 4 and Figure 5, when polished with cationic ceria particles, a significant increase in the polishing rate of the pads of the present invention was observed over the entire downforce range. Depending on the downforce, the present invention provides a 20% to 30% increase in removal rate. The slope of the pressure/rate response is a measure of the pad's Preston coefficient contribution and is at least 60% higher than that of the parent pad. [Table 4] removal rate sample SG (g/cm ³ ) Down pressure: 3 (psi)/20.7 (kPa) (Å/min) Downforce: 4 (psi)/27.6 (kPa) (Å/min) Down pressure: 5 (psi)/34.5 (kPa) Å/min B 0.95 2141 2870 3479 2 0.95 2653 3685 4654

In contrast, as shown in Table 5 and Figure 6, both fluorine-containing samples had lower rates over the entire downforce range when using anionic silica particles. Additionally, the slope of the pressure/rate response, which is a measure of the difference in the pad's Preston coefficient contribution, is significantly higher than that of the parent pad by approximately 10%. [table 5] removal rate sample SG (g/cm ³ ) Down pressure: 3 (psi)/20.7 (kPa) (Å/min) Downforce: 4 (psi)/27.6 (kPa) (Å/min) Down pressure: 5 (psi)/34.5 (kPa) Å/min B 0.80 1684 2449 2895 2 0.80 1602 2116 2707

For the two polishing experiments shown above, total defects after polishing were measured at 3 psi (20.7 kPa). Cerium dioxide polishes were measured after application of HF and EKC 5650 cleaning solution was used for silica polishes. The results are shown in Table 6. Fluorinated formulations showed reduced total defects when polished with ceria, whereas the opposite effect was observed when colloidal silica was used. [Table 6] sample slurry Total defects after polishing (#) B Asahi CES333 635 2 Asahi CES333 470 B SS25 16012 2 SS25 22017 Note: Total defects vary greatly depending on polishing process, slurry, measurement technique and setup. Total defects determined on polished wafers after cleaning with Lam Ontrak Synergy™ cleaner using DuPont™ EKC PCMP5650™ cleaning chemical (1:90 dilution). Cleaned wafers were measured on a KLA/TENCOR Surfscan ^® Sp2 unpatterned wafer defect inspection system (using defect sizes > 0.16 um). Defect data is analyzed using KLA/TENCOR Klarity ^® software.

Example 4

Two forms of the above molecule were used, with n values of 1.5 (fluorinated species, MW approximately 1800 g/mol) and n > 4 (fluorinated species, MW approximately 2000 g/mol). Larger n values will result in increased compatibility of fluorinated segments used in soft segment ureas. To evaluate the effect on polishing, control prepolymers were prepared from the following polyurea formulations. [ Table 7] sample PTME250/PTME650/PTME1000/PTME2000 ( wt% ) Isocyanate NCO ( wt% ) B 29/22.2/24.9/23.9 TDI/H12MDI (80/20 wt ratio) 9.15 PTME = polytetramethylene ether (molecular weight)

A comparative prepolymer was prepared by replacing part of the PTMEG2000 components with ethoxylated perfluoroether, as shown below: [ Table 8] sample R PTME250/PTME650/PTME1000/PTME2000/ ethoxylated perfluoroether ( wt% ) NCO ( wt% ) phase after reaction 5 About 1.9 29/22.2/24.9/11.95/11.95 9.15 liquid 6 About 1.9 29/22.2/24.9/17.95/5.98 9.15 liquid 7 5.3 29/22.2/24.9/11.95/11.95 9.15 solid 8 5.3 29/22.2/24.9/17.95/5.98 9.15 liquid PTME = polytetramethylene ether (molecular weight)

The use of prepolymers with a perfluoroether/ethylene oxide atomic ratio of 1.9 has higher compatibility and can be used to prepare prepolymers that are feasible at both concentrations, while perfluoroether/ethylene oxide An alkane atomic ratio of 5.3 is only feasible at lower concentrations due to excessive phase separation leading to increased viscosity and solidification of the prepolymer. The curing of the prepolymer makes it unsuitable for casting with a curing agent into polyurea polishing pads.

The pad will be cast from a workable formulation using MBOCA as the curing agent (105% stoichiometry). The removal rate results as a function of downforce are shown below. As can be seen from the figure, the fluorinated prepolymer samples all showed improved removal rates over the unfluorinated controls, however, due to the increased compatibility and higher achievable concentration of the ethoxylated perfluoroether, the samples The removal rate of 5 is further improved compared to samples 6 and 8.

The estimated perfluoroether/ethylene oxide atomic ratio for the 3-ethylene oxide fluorinated polymer of samples 7 and 8 was determined to be 5.3. For about 8, the perfluoroether/ethylene oxide atomic ratio of samples 5 and 6 is about 1.9. To improve casting and soft segment separation, the perfluoroether/ethylene oxide atomic ratio is preferably less than 4. More preferably, this ratio is less than 3, and most preferably, it is less than 2.5. Alternatively, surfactants can improve the solubility of high perfluoroether/ethylene oxide atomic ratio formulations. However, these formulations do not always provide additional removal rate increases with the addition of fluorinated polymer. Table 9 below provides ceria polishing rates when using the ceria slurry of Example 3 and the prepolymer cast into a pad as described above. [Table 9] Down pressure (psi)/(kPa) 2/13.8 3/20.7 4/27.6 5/34.5 Sample B (Å/min) 3037 4649 5838 6851 Sample 6 (Å/min) 3171 5161 6928 8085 Sample 8 (Å/min) 3216 5020 6964 7975 Sample 5 (Å/min) 3547 5816 7841 9545

As can be seen from Table 9, the fluorinated polymer additive provided increased downforce at higher downforce when using modified ceria slurry Hitachi HS-08005A diluted 1:9 at pH 8.35. removal rate.

Sample 7 prepolymer can be prepared by adding 0.5 wt% of the total prepolymer Merpol A alcohol phosphate surfactant to the mixture prior to reaction. This makes it possible to cast pad samples. However, no further improvement was observed by increasing the atomic ratio R to 5.3 using surfactants, unlike the atomic ratio R of 1.9 observed by comparing it to Sample 5 above. [Table 10] Down pressure (psi)/(kPa) 2/13.8 3/20.7 4/27.6 5/34.5 Sample 7 (Å/min) 3052 4958 6931 8068 Note: The polishing data in Table 10 is from the same ceria modified slurry used in Table 9.

The polyurea-terminated fluorinated polymers of the present invention provide unexpected improvements in dielectric removal rates when polishing using ceria-containing slurries or modified ceria-containing alkaline slurries at acidic pH levels. . Furthermore, the fluorine-rich phase aggregates near the microspheres, forming a heterogeneous mixture microstructure. Additionally, the fluorine-rich phase accumulates near the surface to increase the polishing rate. Finally, the microspheres near the surface can be compressed and flattened to form a polished layer with a small tooth-like micro-texture.

without

[Fig. 1] is a schematic diagram of a SIMS TOF compilation of the fluorine-rich area of the polishing pad of the present invention, which is converted into a black and white scale, where the solid black area represents the background without the polishing pad.

[Fig. 2] is a cross-sectional SEM of a used polishing pad of the present invention, showing that polymer microelements adjacent to the polishing surface collapse without being punctured by a diamond dresser.

[Figure 3] is a higher magnification cross-sectional SEM of a used polishing pad showing collapse of the polymer microelements adjacent to the polishing surface without being punctured by the diamond dresser.

[Figure 4] is a cross-sectional SEM of a used polishing pad, showing the formation of a small tooth-like polishing surface.

[Figure 5] shows a comparative ceria slurry polishing test of a pad of the present invention and a pad made from a fluorinated polymer-free matrix formulation.

[Figure 6] shows a comparative silica slurry polishing test of pads of the present invention and pads made from a fluorinated polymer-free matrix formulation.

without

Claims (10)

A polishing pad suitable for polishing at least one of a semiconductor, optical, magnetic or electromechanical substrate, comprising: Polyurea polishing layer, the polyurea polishing layer includes a polyurea matrix, the polyurea matrix has a soft phase and a hard phase, the soft phase is formed by soft segments, and the hard phase is composed of diisocyanate hard segments and cured The soft segment is a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon having a length of at least six carbons, the polyurea matrix is cured by the curing agent and contains a gas or liquid filled A polymeric microelement, the soft segment forms a fluorine-rich phase that accumulates during polishing adjacent the polymeric microelement and the polishing layer, wherein the polishing layer remains hydrophilic during polishing under shear conditions. The polishing pad of claim 1, wherein the fluorine-rich region creates regions of higher and lower fluorine concentrations around the polymeric microelements. The polishing pad of claim 1, wherein the thickness of the fluorine-rich phase adjacent to the microsphere is less than fifty percent of the average diameter of the polymer microelement. The polishing pad of claim 1, wherein the polymeric microelements fracture under compression adjacent the polishing slurry independent of diamond conditioning. The polishing pad according to claim 1, wherein the polishing layer can form a surface containing a small tooth structure during polishing. A polishing pad suitable for polishing at least one of a semiconductor, optical, magnetic or electromechanical substrate, comprising: Polyurea polishing layer, the polyurea polishing layer includes a polyurea matrix, the polyurea matrix has a soft phase and a hard phase, the soft phase is formed by soft segments, and the hard phase is composed of diisocyanate hard segments and cured and wherein the hard phase is precipitated in the soft phase, the soft segment is a copolymer of aliphatic fluorine-free polymer groups and a fluorocarbon having a length of at least six carbons, the polyurea matrix is formed by The curing agent solidifies and contains gas or liquid filled polymeric microelements, the soft segments form during polishing a fluorine-rich phase that accumulates adjacent the polymeric microelements and the polishing layer, wherein the polishing layer under shear conditions Remains hydrophilic during polishing. The polishing pad of claim 6, wherein the fluorine-rich region creates regions of higher and lower fluorine concentrations around the polymeric microelements. The polishing pad of claim 6, wherein the thickness of the fluorine-rich phase adjacent to the microsphere is less than fifty percent of the average diameter of the polymer microelement. The polishing pad of claim 6, wherein the polymeric microelements fracture under compression adjacent the polishing slurry independent of diamond conditioning. The polishing pad according to claim 6, wherein the polishing layer can form a surface containing a small tooth structure during polishing.